There are known polyurethanes characterized by the presence, in their structure, of polyoxyperfluoroalkylene blocks deriving from the use of perfluoropolyethers with hydroxylated end groups. Products of such type are described in particular in Italian Pat. No. 903446: they are characterized by a glass transition temperature (Tg) lower than -78.degree. C. and therefore they retain flexibility and elastic properties even at very low temperatures. The fluorinated polyurethanes known so far, however, do not possess in the whole optimum mechanical characteristics as regards hardness, tensile strength, elastic modulus, elongation.